Field of the Invention
The present invention relates to a water heating apparatus, and more particularly to a water heating apparatus having a function of detecting scale clogging.
Description of the Background Art
Use of a water heating apparatus for a long time causes a scale to adhere in a pipe of a heat exchanger. In particular, in the case where so-called hard water containing a large quantity of calcium ion and magnesium ion is used, the amount of adhesion of the scale becomes greater. When use of the water heating apparatus with adhesion of the scale continues, normal heat transmission of the heat exchanger may be impaired by the scale, thus damage such as cracks in the heat exchanger may occur due to generation of thermal stress caused by the scale. Therefore, it is necessary to implement cleaning for removing the scale at an appropriate time. Operation controls related to detection of a scale in water heating apparatuses are disclosed in the following PTDs 1 to 5.
According to PTD 1 (Japanese Patent Laying-Open No. 2013-160488), a water heating apparatus prohibits a hot water supplying operation at the time of occurrence of a heat transmission inhibiting factor caused by adhesion of a scale and the like, and also notifies the event. When a predetermined operation is performed, the water heating apparatus cancels the prohibition of the hot water supplying operation.
According to PTD 2 (Japanese Patent Laying-Open No. 2004-169930), a water heating apparatus assumes a life duration of a heat exchanger by monitoring combustion performance. When the life duration has come to end, the water heating apparatus notifies the event. According to PTD 3 (Japanese Patent Laying-Open No. 2003-254615), a water heater notifies an error when it detects scale clogging and the like in a heat exchanger. Then, the water heater eventually stops combustion.
According to PTD 4 (Japanese Patent Laying-Open No. 2010-261651), a water heating apparatus detects occurrence of scale clogging by detecting a temperature at an outlet of a heat exchanger.
According to PTD 5 (Japanese Patent Laying-Open No. 2012-77990), a latent heat recovery type water heater discharges a drain generated in the water heater to a bathroom using a re-heating pipe and thereafter cleans the re-heating pipe, and notifies the event of cleaning at that time.